1. Field
The present application relates to lighting devices including an orange-red phosphor with co-dopants. The present application also relates to phosphor compositions including an orange-red phosphor with co-dopants and methods of using the same.
2. Description
Solid state light emitting devices, such as light emitting diode (LED), organic light emitting diode (OLED) or sometimes called organic electroluminescent device (OEL), and inorganic electroluminescent device (IEL), are widely utilized for various applications such as flat panel displays, indicator for various instruments, signboards, and ornamental illumination etc. Improving the efficiency of these light emitting devices, especially LED, may provide higher luminescence intensities suitable for general purpose lighting, which replaces current fluorescent and incandescent lamps. A white-LED, especially with a high color rendering index (CRI) and low correlated color temperature (CCT), shows promise as a replacement for existing general purpose lighting devices.
Conventionally, white-LED includes the combination of blue-LED and yellow light emitting YAG phosphor powder dispersed in an encapsulating resin, such as an epoxy or silicone (see e.g, U.S. Pat. Nos. 5,998,925 and 6,069,440). However, this YAG:Ce type LED system exhibits low CRI due to the lack of red luminescence. Accordingly, new red phosphors have been proposed to improve the red luminescence, but most of these red phosphors exhibit poor absorption when excited by traditional blue LED light sources. Meanwhile, red phosphors exhibiting blue excitation face a variety of problems. For example, the synthesis of many blue-excitable red phosphors is expensive because it requires high pressures and/or special ambient controls. Also, many blue-excitable red phosphors degrade when exposed to moisture or increased temperatures. Thus, the production of red phosphors remains a major challenge.
For a warm white LED study, the deep-red color rendering R9 is particularly useful for identifying the emission strength in the deep red region. In the field of solid-state lighting, R9 is an important challenge, and any level of improvement on R9 has an impact on warm light study and application (G. Cheng, M. Mazzeo, S. D'Agostino, F. Della Sala, S. Carallo, and G. Gigli, “Pure white hybrid light-emitting device with color rendering index higher than 90,” Opt. Lett. 35, 616-618 (2010)).